Use of private data variables in simple POJO [duplicate]-CodePudding

Recently I was going through the concept of Encapsulation in Java. I was wondering if making data variables private along with public setter methods really make sense in simple POJO class? Please refer below POJO:

public class Employee{
    
    private String id;
    private String name;
    private String department;
    private int age;
    
    public Employee(){        
    }

    public Employee(String id, String name, String department, int age){
        this.id = id;
        this.name = name;
        this.department = department;
        this.age = age;
    }
 
    public String getId() {
        return id;
    }
 
    public void setId(String id) {
        this.id = id;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public String getDepartment() {
        return department;
    }
 
    public void setDepartment(String department) {
        this.department = department;
    }
    
    public int getAge() {
        return age;
    }
 
    public void setAge(int age) {
        this.age = age;
    }
  
}

I mean why am I making the name variable private when I can anyway change it using the setter method?

CodePudding user response：

In the general case, it'll be the very basic

    public void setName(String name) {
        this.name = name;
    }

Where it's identical to just doing employee.name = "william hammond". But imagine a case where you'd like to do implement something like a private String normalize(string username) method where you maybe make it all lower case, check for a valid name or prevent unicode entries. If you make name public initially you'll have users doing employee.name = "whatever they want :) 123" and you'll lose the ability to enforce that constraint.

Also see Why use getters and setters/accessors?

CodePudding user response：

Using getters/setters is just considered good practice, but it can often be overkill - like in your example.

If you have methods that mutate the variable before setting, then it's nice to have getters/setters for the basic fields as well to maintain consistent code style.

Here's a good article on it: https://dzone.com/articles/getter-setter-use-or-not-use-0

CodePudding user response：

Let's have an example:

public class Example {
    private String firstName;
    private String lastName;

    public Example(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }

    public String getFirstName() {
        return firstName;
    }

    public String getLastName() {
        return lastName;
    }
    
    public String getFullName() {
        return firstName   " "   lastName;
    }
}

This class has 3 properties (firstName, lastName, fullName), but only two fields (firstName, lastName). It makes sense, because a full name can be retrieved by combining first and last name.

However, I've noticed that I call getFullName() a lot of times in my program, but I almost never call getFirstName() and getLastName(). This slows down my program, because I need to create a new string each time getFullName() is called. So, I've refactored my code to have a better performance:

public class Example {
    private String fullName;

    public Example(String firstName, String lastName) {
        this.fullName = firstName   " "   lastName;
    }

    public String getFirstName() {
        return fullName.split(" ")[0];
    }

    public String getLastName() {
        return fullName.split(" ")[1];
    }
    
    public String getFullName() {
        return fullName;
    }
}

Now my code works faster when calling getFullName(), but slower when calling getFirstName() and getLastName(), however It's exactly what I needed. From outside the class, nothing really've changed.

As you can see by the given example, fields describe how your class uses the computer's memory, but not necessarily which properties your class has. This is why fields should be considered an implementation detail and therefore be private to a class.